Centering device



Dec. 5, 1944. J. P. FRANCESCO 4 GENTERING DEVICE Fi'led March 27, 1943INVENTOR Jblm 7. Francesca.

Patented Dec. 5, 1944 UNITED STATES PATENT OFFICE" CENTERING DEVICE JohnP. Francesco, Havel-hill, Mass. Application March 27, 1943, Serial No.480,879

2 Claims. (Cl. 33-46) (Granted under the act of March 3, 1883, asamended April 30, 1928; 370 0. G. 757) In drydocking operations, it isusually necessary to maintain the ship over the centerline of thedrydock floor so that the keel will drop on the keel line pier blocks asthe water level goes down. After the ship is moved in position in theflooded drydock, centering lines are, stretched across the dock at thebow and stem to properly guide the ships downward course as the waterrecedes. A float or plumb bob is commonly used on this line as a markerover the center line of the dock, and as the ship is lowered thecentering line is let out at both ends to more or less follow the dropin water level. i

Another method that has sometimes been used is to have a buoyant markerat the bow or stern attached to a line running down under a pulleyfastened to a pier block properly located on the dock floor, the otherend of the line being passed up to the top of the dock where it is takenup as the water recedes, so as to maintain it taut between the floatingmarker and the pulley while maintaining the marker on the water surface.This forms a virtual inverted plumb bob supported upward from thepulley, the buoyant force taking the place of the force of gravity in anactual plumb bob or rod.

The present invention is an improvement in the means heretofore used forcentering and checking the ships position in a drydock by combining thetwo old devices and connecting them together to aid in maintaining theship on its proper downward course as the water is drawn off, so that itwill come to rest in proper central alignment on the keel line pierblocks.

The object of this device is to provide an improved means for sightingthe bow or stem of a ship in drydocking to enable its proper guidanceover the centerline of the dock as the water is withdrawn therefrom.

A further object is to combine the devices used to assist in centering aship in drydock in such a manner asto obtain better results andeliminate any efiect of turbulent weather conditions that are sometimesmet with.

A further object is to devise a centering means for ships in drydocking,which may be easily drawn out of the way of the ship as it is moved intoplace, and which may then be quickly and accurately adjusted and usedfrom then on without any further adjustment.

Further and more specific objects of my device will appear as thedescription proceeds, having reference to the accompanying. drawing, inwhich:

Fig. 1 is a sketch indicating the, relative location of the centeringmeans in connection with a particular shape of ship which comes to apoint at one place at the bow and at two places at the stern;

Fig. 2 is a side view sketch of the ship and ceitering device shown inFig. 1 from the port s1 e;

Fig. 3 is a sectional view of a portion of the drydock taken at 1-3 ofFig. 1, showing the relative positions of the parts of the device, thekeel line pier block being enlarged for better illustration, and

Fig. 4 is another sectional view of a portion of the drydock taken at3-3 of Fig. 1, showing the keel line block and another pier block,enlarged as in Fig. 3, but omitting the plumb bob line 9, and showing abuoy attached to the sight line used as a part of my device.

Like parts in the several views of the drawing are designated by thesame numerals.

In the drawing, the ship I is seen moved into position over the drydockfloor center line l2 (Fig. 1). The line 9 is stretched across thedrydock at the bow and has a plumb rod I hung on a ring 8 fixed to theline 9', over the center line It. Similar lines 8' and 9" are stretchedacross the drydock and have plumb rods 1' and 1" adjacent thecorresponding comers at the stern.

(If the stern comes to a point at one place, only one line would be usedat the stem, with a plumb rod I at that point.)

The {pier block II is on the center line of the drydock floor and has amark in on its top designating the line directly over the center line.The pulley 2 is mounted so that its groove on the port side is tangentto the vertical plane of this centerline. The sight line 4 is passedaround the pulley,

as shown more clearly in Figs. 3 and 4, so that it runs to the starboardside of the pulley and is fastened to line 5 which is passed around apulley 3 mounted on a block l3 at some distance from block II, and thenpasses up to the top of the drydock, where it is held or fastened tokeep the line taut. The other end of the sight line 4 is connected to abuoy 8.

To prevent fouling of the sight line during maneuvers of the ship inmoving it into position, the buoy may be pulled down out of the way bypulling up the line 5. When the ship is in place, line 5 is let outuntil the buoy comes to the surface. It is then picked up by some one ina punt, and the sight line 4 is removed from the buoy and attached tothe ring 8 which is directly over the drydock centerline, as previouslypointed out. The line 9 may thenbe drawn up as desired so that the ring8 remains in the vertical plane of the centerline, and the line may bealso drawnlisting the ship might have which would bring its keel offcenter even if one particular portion of the how were kept centeredduring the ship lowering operation.

Thus the device enables proper alignment of the keel on the keel blockseven if the ship lists. The device has the further advantage overpreviously used devices for this purpose in that it is more stable andneeds no further adjustments once it is set up. The line 9 if used byitself with a plumb bob or even a plumb rod, which may be 2 or 3 feetlong, would not be as accurate nor stable as my combined device. A highwind or heavy sea, if the rod extends partly into the water, would tendto sway it and make sighting difficult and inaccurate. The same is trueif the buoy and sight line 4 is used independently for sightingpurposes.

In addition to being unstable, these devices when used independently,require constant adjustment during the water evacuation. As the ship islowered, they have to be accordingly lowered. Line 5 would have to bepulled up to keep the sight line 4 taut, with the buoy following thewater level. In the case of the line 9, its ends would have to be letout proportionally to maintain the ring 8 and the plumb rod directlyover the center line during the lowering operation.

In my device by attaching the sight line It to the ring 8, I obtain astable device that is simpler to adjust, and once adjusted may then beleft alone and used to better advantage, making sighting easier and moreaccurate, not only in determining the proper centering of the ship atthe surface of the water, but also with respect to its keel.

Similar sight lines 4' and 4" are arranged in like manner at the stem atthe corresponding points thereof, locating the ships stern over thecenterline. It is to'be understood that a single sight line 4' may beused at a point of the stern which is directly over the keel line, ifdesired. In either case the sight lines 4" and/or 4' are connected tothe corresponding line or lines 9" and/or 9' in a manner similar to themethod used at the bow, as explained above.

(9 I may omit any one or all of the pulleys 3, 3' and 3" whereconditions are such that the line passed directly up from the pulley 2to the top of the dock would not interfere with the ship maneuvers, inbringing it into position. Pulley 3 (or 3' or 3") is used and placed 011to one side only under conditions where it is necessary to do this toprevent fouling of the line.

It may therefore be seen that my device will save time to a certaindegree and will give more satisfactory results in operation.

This device and method may be used by or for the Government of theUnited States for governmental purposes without the payment to me of anyroyalties thereon or therefor.

What is claimed is: 1. A ship centering device for drydocks comprising aline stretched across the drydock at either end of the ship having aplumb bob hung at a fixed point thereon adjacent the position of theship to be sighted when the ships keel is properly aligned over the keelline pier blocks, a sight line having one end thereof tied to the plumbbob, the other end of said sight line being passed under a pulleylocated directly under said plumb bob and then to the top. of thedrydock for fastening thereto.

2. A centering device for use in drydocks including a line stretchedacross the top of the drydock, another line extending from the top ofthe drydock and passed under a pulley mounted adjacent the floor of thedrydock over its center line, and means at the point of thefirst-mentioned line directly over the centerline of the drydock floorto which the said other line is tied, so as to form a stable verticalsight line.

JOHN P. FRANCESCO.

